libertus

~

Posted on Wed, 25th January 2006 at 12:27 under Software, Eureka!

The may be operator. A syntax for expressing a conditional cause chain or known sequence of expressions likely to resolve to a single value. Akin to the SQL function COALESCE().

PHP example

Expression without may be operator:

if( !isset( $id ) )
   if( isset( $_COOKIE['id'] ) )
      $id = $_COOKIE['id'];
   else
      if( isset( $_POST['id'] ) )
         $id = $_POST['id'];
      else
         if( isset( $_GET['id'] ) )
            $id = $_GET['id'];
         else
            $id = -1;

Expression with may be operator:

$id ~ $_COOKIE['id'] ~ $_POST['id'] ~ $_GET['id'] ~ -1;

Or, if you want to be fancy, declare a dimension (thanks Larry):

$id ~_['id']~ $_COOKIE ~ $_POST ~ $_GET ~ -1;

And, if Larry is reading, another tribute to him, a functional dimension:

$id ~is_numeric(_['id'])~ $_COOKIE ~ $_POST ~ $_GET ~ -1;

Enigmatic? Me?

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3 Responses

Libertus said: January 25th, 2006 at 13:08

This isn’t an original idea. I’m sure I’ve borrowed the concept from another language somewhere, but memory fails as to which one.
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Libertus said: January 25th, 2006 at 17:56

I’m beginning to explore, once again, the possibilities afforded by interpreted over compiled languages. The ~ operator is little more than a pattern-based code generator, My functional dimension above raises an ‘orrible ambiguity - does $id become the result of the is_numeric() function or the value passed? In the case above, the answer has to be the return value of the function. What I really want is the value passed to the function, if the function succeeds with that value.
```
$id ~_['id']?is_numeric(_)~ $_COOKIE ~ $_POST ~ $_GET ~ -1;
```
Not quite so easy to read now, but expresses the conditional nature of the materialisation and the dimension.
Reply
Libertus said: January 25th, 2006 at 18:00

Would $ be better than _ as the placeholder in the dimensional syntax?
```
$id ~ $['id'] ? is_numeric($) ~ $_COOKIE ~ $_POST ~ $_GET ~ -1;
```
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~

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